Early this year I made a corian armboard and mounted a Grace 707 arm to a Denon DP72L table. I have used it since with no problems. Today I hooked up some used tube mono blocks I recently purchased and my turntable channel suddenly has a very noticeable hum. The CD player is dead quiet. I have a Dodd tube phono stage and also a Dodd battery preamp. The only thing I did different was change amps (previously used a S.A.E. Mark IIIa with no hum on this TT whatsoever) and also changed the physical set up of my gear on my stand. When I used the S.A.E., I previously had the ground wire from the Grace arm going to the Dodd preamp, but when I got the hum I changed the ground wire to connect to the Belkin PF 60, but it made no difference in the hum. The amps have no ground connection for a TT per se. Any thoughts would be greatly appreciated. The sound is awesome but this hum is very frustrating.